Heavy-duty truck brake technology has advanced over the years and continues to be an important safety feature for trucks and trailers. All brakes are not created equal, however, so it is important to understand the differences.
There are two types of air brakes: disc brakes and drum brakes. Though both types use the same principles of friction to slow a vehicle down, air disc brakes have many advantages over drum brakes.
The trucking industry is trending toward air disc brakes because of safety, efficiency, and in some situations, a lower total cost of ownership. Disc brakes enhance safety by providing shorter stopping distances than drum brakes and improving trailer in-line braking stability. The stopping distance for disc brakes can be 25 to 30 feet less than drum brakes, depending on tires, speed, conditions and the braking system on the tractor. The stopping power is noticeably greater when both the tractor and trailer are equipped with air disc brakes, particularly when the vehicle is traveling at increased speeds.
Disc brakes require less maintenance than drum brakes, because they provide stable and uniform braking, which helps brake components last longer. This means they provide superior braking efficiency and remain in optimum adjustment.
Additionally, service intervals are generally longer for disc brakes than drum brakes, and service technicians can change disc brake pads in 25 percent of the time it takes to change a drum brake shoe.
While disc brakes typically have a higher upfront cost than drum brakes, they can have a lower total cost of ownership.
Consider the following factors:
- Longer service intervals and shorter service times equal lower maintenance costs and more uptime for the trailer
- Rust jacking, which is common on drum brake shoes, is virtually eliminated with disc brakes
- Disc brakes eliminate the need for S-cams, slack adjusters, brake drums, brake shoes and bushings, rollers and springs in a parts maintenance inventory
- Disc brakes reduce the chance of CSA brake violations for brakes out of adjustment, which can put the trailer out of service
The Bottom Line
Though the upfront cost may be higher, spec’ing a trailer with air disc brakes can increase the overall safety and efficiency of the trailer. Great Dane continues to work with disc brake providers so we can offer this option competitively as more customers move to this style of foundation brake.
Drum Brakes vs. Disc Brakes: How They Work
Drum brakes have friction material riveted to brake shoes. When the brake is applied, the brake shoes push outward, rubbing against the inside of the drum and slowing the wheel. Over time, the friction material wears away and the automatic slack adjuster compensates for the loss of brake shoe lining thickness. Eventually, the slack adjuster reaches a limit and the brake shoes must be replaced.
Disc brakes have friction pads that float inside the caliper adjacent to a large metal disc called a rotor. Instead of a brake drum attached to the wheel hub, a rotor is attached to the hub. A caliper is contained on the brake carrier with its own brake chamber. When the brake is applied, the caliper squeezes the brake pads against the rotating rotor, slowing the wheel. Since the rotor is exposed to outside air, it is able to cool quickly, which decreases its tendency to overheat or cause fading.